new (to me) Kenwood KA 8100 Chapter 2

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by rbspop, Sep 9, 2017.

  1. rbspop

    rbspop rbs55pop Subscriber

    Messages:
    82
    Location:
    Reno, NV
    Thanks to the many who helped I now have the 8100 up and running ( replaced caps, zeners, Qi13, 14) and it sounds really good (much better than it did). Next I will start on the Power Amp Unit (I replaced the main filter caps while doing the control amp). I plan on changing the trimmers and:

    "Main board (power amp board):


    De1,2 (EQA01-24R) to 1n5252B 24V zeners
    De3,4 (EQA01-30R) to 1n5256B 30V zeners
    De16,17 (W06B) to 1n4007

    Protection circuit
    Qe31 (relay driver - 2sc1735) to KSC2690AYS
    Qe29 (2sc1222) to KSC1845
    Qe30 (2sc1681) to KSC1845"

    Thanks for this list goes to Gort69 ..

    I have; however, run into a small(?) problem in that while turning the Center Voltage
    Trim pots .. nothing happens? I am doing the adjustment according to page 14 of the service manual??

    Also the Bias on the left channel is 14mv (per spec) while the best I can get on the right channel is 29mv and this is after one hour of running??
     
  2. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    828
    Location:
    Vancouver, WA
    Center voltage (DC offset)

    Since neither trimmer has any effect I'd guess you're doing something wrong.

    - meter set to read DC milivolts (if not an auto-ranging meter)

    - speakers disconnected, red lead to LEFT speaker A+, black lead to LEFT speaker A-

    - speaker selector set to A, volume at minimum, tone controls set to "0" or turnover switches set to defeat, balance at center

    - selector switch set to tuner or aux, and nothing connected to those input jacks

    - power up, relay click and note reading.

    - after a few minutes, adjust trimmer Vr1 (left rear) to read 0mv

    - power off, move meter leads to A speakers RIGHT channel, power up, wait, adjust Vr2 (right rear) to read 0mv
     
  3. rbspop

    rbspop rbs55pop Subscriber

    Messages:
    82
    Location:
    Reno, NV

    Okay .. I get a DOH! moment. I always listen thru headphones and forgot to set the speaker switch.

    Now Offset is within 0.2 mv on both channels and Bias is 14.2 on both (give or take some fluctuation) .

    I can't thank you enough gort69 ..
     
  4. mcfl

    mcfl Member

    Messages:
    96

    Do you mind sharing the part list for the caps
     

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